Virtual image display device and optical unit

The present application is based on, and claims priority from JP Application Serial Number 2024-038756, filed Mar. 13, 2024, the disclosure of which is hereby incorporated by reference herein in its entirety.

The present disclosure relates to a virtual image display device and an optical unit that enable observation of a virtual image, and particularly, to a non-see-through type virtual image display device and the like.

A known virtual image display device includes an image element that displays an image, a first optical unit disposed at a position where image light is extracted, a second optical unit disposed closer to the image element than the first optical unit, a Fresnel-type half mirror formed at a bonding portion between the first optical unit and the second optical unit, and a transmission/reflection selection member provided on a light emission side of the first optical unit and selectively transmitting and reflecting light in accordance with the polarization state of light (JP-A-2020-24246).

In the device disclosed in JP-A-2020-24246, since the Fresnel-type half mirror is incorporated between the first optical unit and the second optical unit, the surface shape of the optical unit becomes complicated, and there is a possibility that image formation will be deteriorated when light is reflected by or passes through the half mirror.

Although the device disclosed in JP-A-2020-24246 uses a flat plate having a Fresnel-type lens embedded therein as an imaging system, it is also conceivable to use a meniscus lens instead of the flat plate. However, when the meniscus lens is used instead of the flat plate, a ¼ wave plate configuring a transmission/reflection selection member is formed at a curved surface, birefringence characteristics of the ¼ wave plate change due to the curvature, and there is a possibility that a desired phase difference effect will not be obtained. In addition, when the ¼ wave plate is attached, there is a possibility that birefringence characteristics will be affected.

A virtual image display device according to one aspect of the present disclosure includes a display that emits circularly polarized image light, and an optical member that folds back the image light twice by reflection to form a virtual image, in which the optical member includes a lens member, a transmissive reflective optical element that is provided facing a first optical surface of the lens member that is close to the display, a reflective polarizing optical element that is provided facing a second optical surface of the lens member that is far from the display and reflects image light, that is linearly polarized light in a first polarization direction, and a wave plate that is provided between the reflective optical element and the polarizing optical element, is formed of a liquid crystal material, converts the image light having passed through the reflective optical element into linearly polarized light in a first polarization direction, and converts the image light, that is reflected by the reflective optical element to reciprocate, into linearly polarized light in a second polarization direction.

1 3 FIGS.to A virtual image display device of a first embodiment of the present disclosure will be described below with reference to.

1 FIG. 1 FIG. 200 200 200 200 is a perspective view showing a mounted state of a head-mounted display, that is, a head-mounted display device. The head-mounted display device (hereinafter, also referred to as an HMD)allows an observer or a wearer US who wears the HMDto recognize a video as a virtual image. Inand the like, X, Y, and Z represent a rectangular coordinate system. The +X direction corresponds to a lateral direction in which both eyes EY of the observer or the wearer US, who wears the HMD, are arranged. The +Y direction corresponds to the upper direction perpendicular to the lateral direction from the viewpoint of the wearer US in which both of the eyes EY are arranged. The +Z direction corresponds to the forward direction or the front side direction from the viewpoint of the wearer US. The +Y direction is parallel to the perpendicular axis or the perpendicular direction.

200 100 100 100 100 100 90 100 102 103 100 102 103 200 100 100 100 103 103 102 102 102 102 102 a a b b a b a b a b The HMDincludes a first virtual image display deviceA for a right eye, a second virtual image display deviceB for a left eye, a pair of templesC that support the virtual image display devicesA andB, and a user terminalbeing an information terminal. The first virtual image display deviceA is configured with a first display drive unitdisposed in an upper portion and a first display optical systemthat covers the area in front of the eyes. The second virtual image display deviceB is configured with a second display drive unitdisposed in an upper portion and a second display optical systemthat covers the area in front of the eyes. The HMDobtained by combining the first virtual image display deviceA and the second virtual image display deviceB together is also a virtual image display device in a broader sense. The pair of templesC support the upper ends of the pair of display optical systemsandvia the display drive unitsandthat are integrated in appearance. A combination of the pair of display drive unitsandis referred to as a driving device.

2 FIG. 103 103 10 20 80 10 a a is a conceptual side view showing the structure of the first display optical system. The first display optical systemincludes a displaythat emits circularly polarized image light ML, an optical memberthat folds back the image light ML twice by reflection to form a virtual image, and a circuit memberthat controls operations of the displayand the like.

100 80 10 20 100 In the first virtual image display deviceA, the optical device excluding the circuit member(specifically, the displayand the optical member) will be referred to as an optical unit.

103 103 103 103 103 b a a a b Although detailed description will be omitted, the second display optical systemis optically identical to the first display optical system, or is a left-right inverted version of the first display optical system. In the following, the first display optical systemwill be described, and description of the second display optical systemwill be omitted.

103 103 10 20 a b In the case of the display optical systemsandshown in the drawing, FOV120° is achieved, and a distance from the displayto an emission surface at the rear end of the outer edge of the optical memberis 13 mm.

103 10 11 1 11 a In the first display optical system, the displayincludes an image display panelthat is a self-luminous image light generation device, and a polarizing control member PCthat converts the image light ML emitted from the image display panelinto circularly polarized light.

11 11 11 11 80 11 d The image display panelis, for example, an organic electroluminescence (EL) display, and forms a monochrome or color still image or moving image on a two-dimensional display surface. The image light ML emitted from the image display panelincludes randomly polarized light. The image display panelis driven by the circuit memberto perform a display operation. The image display panelis not limited to the organic EL display, and can be replaced with a display device using inorganic EL, an organic LED, an LED array, a laser array, a quantum dot light emission element, or the like.

11 The image display panelis not limited to a self-luminous image light generation device, and may be configured with an LCD or any of other light modulation elements and form an image by illuminating the light modulation element with a light source such as a backlight.

1 14 15 11 The polarizing control member PCincludes a linear polarizing plateand a ¼ wave platein this order from the image display panelside.

14 11 14 15 14 The linear polarizing plateis, for example, an absorption-type polarizing plate, and selectively transmits only second linearly polarized light (horizontally polarized light) in the X direction which is the horizontal direction in the present embodiment. That is, only linearly polarized light in the X direction of the image light ML emitted from the image display panelpasses through the linear polarizing plateand is incident on the ¼ wave plate. The linear polarizing platehas a sheet shape, and is manufactured by stretching a film in which a dichroic dye such as iodine is impregnated into polyvinyl alcohol (PVA) in a certain direction.

15 14 1 15 14 11 11 15 11 15 c c The ¼ wave platehas its main axis or fast axis set between the vertical and horizontal directions, that is, between the Y direction and the X direction, and converts the second linearly polarized light (horizontally polarized light) that has passed through the linear polarizing plateinto, for example, right-handed circularly polarized light C. The ¼ wave plateis formed of, for example, a liquid crystal material such as a photo-crosslinkable polymer liquid crystal material, but may be formed by processing a birefringent crystal material such as quartz into a thin plate. As a specific manufacturing method, the linear polarizing plateis provided on a cover glassof the image display panel, and the ¼ wave platemade of a UV-curable photo-crosslinkable polymer liquid crystal material is provided thereon. The photo-crosslinkable polymer liquid crystal material is applied onto the cover glassby spin coating, ink jet, or the like while controlling the film thickness thereof, and then irradiated with polarized ultraviolet light and baked to function as the ¼ wave plate.

20 2 21 3 11 The optical memberincludes a polarizing control member PC, a lens member, and a polarizing control member PCin order from the image display panelside.

20 The number of lenses configuring the optical memberfor image formation is one, which is an extremely optically simple configuration. In addition, since it can be configured with one lens, the number of components is simply reduced, and further, a process of bonding lenses together is not required, and thus it is possible to greatly reduce the cost as compared with a configuration of the related art. As a result, the weight of the entire optical system can be extremely reduced.

20 2 22 124 11 3 224 25 21 In the optical member, the polarizing control member PCincludes a reflective optical elementand a first wave platein order from the image display panelside. The polarizing control member PCincludes a second wave plateand a reflective polarizing optical elementin order from the lens memberside.

2 22 22 22 22 22 In the polarizing control member PC, the reflective optical elementis a transmissive mirror HM, and partially transmits and partially reflects the image light ML. The reflective optical elementcovers a pupil position PP at which the eye EY or the pupil is disposed, has a concave shape toward the pupil position PP, and has a convex shape toward the outside. The reflectance of the reflective optical elementwith respect to the image light ML is set to, for example, approximately 50% from the viewpoint of securing the luminance of the image light ML, but is not limited thereto. The reflective optical elementis a single layer film or a multilayer film of a metal such as Al or Ag with an adjusted film thickness. The reflective optical elementcan be formed by stacking using vapor deposition, for example, but can also be formed by attaching a sheet-like reflective film.

124 21 1 124 124 The first wave platehas its main axis or fast axis set between the vertical and horizontal directions, that is, between the Y direction and the X direction, and converts circularly polarized light having passed through the lens member, for example, right-handed circularly polarized light C, into elliptically polarized light. The first wave plateis formed of a liquid crystal material such as a photo-crosslinkable polymer liquid crystal material. The first wave plateis a film-like wave plate having flexibility, and is specifically formed of an ultraviolet-curable photo-crosslinkable polymer liquid crystal material.

21 21 21 21 21 21 21 22 21 21 124 21 22 21 22 25 21 21 224 21 25 21 25 a b a b a a a a b b b b The lens memberis a concavo-convex lens having a positive power, and has a first optical surfaceon the incidence side and a second optical surfaceon the emission side. The first optical surfaceand the second optical surfaceare curved surfaces, and specifically, spherical surfaces or aspherical surfaces. The lens membermay be formed of, for example, a resin, but may also be formed of glass. The lens memberformed of glass is advantageous from the viewpoint of miniaturization. The reflective optical elementis provided facing the first optical surface, and more specifically, is indirectly formed at the first optical surfacevia a thin film-like first wave plate. That is, although the first optical surfaceand the reflective optical elementhave the same shape, the first optical surfacefunctions as a convex refractive surface, and the reflective optical elementfunctions as a concave reflective surface. On the other hand, the polarizing optical elementis provided facing the second optical surface, and more specifically, is formed at the second optical surfacevia a thin film-like second wave plate. That is, although the second optical surfaceand the polarizing optical elementhave the same shape, the second optical surfacefunctions as a concave refractive surface, and the polarizing optical elementfunctions as a convex reflective surface.

3 224 124 224 224 21 1 224 224 In the polarizing control member PC, the second wave platehas its main axis or fast axis set between the vertical and horizontal directions, that is, between the Y direction and the X direction, and the retardation of a combination of the first wave plateand the second wave platecorresponds to that of a ¼ wave plate. That is, the second wave plateconverts the elliptically polarized light having passed through the lens memberinto first vertically polarized light Lin a first polarization direction corresponding to the vertical direction or the Y direction which is the perpendicular direction. The second wave plateis formed of a liquid crystal material such as a photo-crosslinkable polymer liquid crystal material. The second wave plateis a film-like wave plate having flexibility, and is specifically formed of an ultraviolet-curable photo-crosslinkable polymer liquid crystal material.

124 224 124 224 21 21 21 124 224 124 224 21 21 21 a b a b Manufacture of the first wave plateand the second wave platewill be briefly described. For example, a photo-crosslinkable polymer liquid crystal material is applied onto a flexible transparent resin substrate to form a photo-crosslinkable polymer liquid crystal material layer, that is, a thin film. By irradiating the thin film of the photo-crosslinkable polymer liquid crystal material with linearly polarized ultraviolet light having a controlled polarization direction, it is possible to control the alignment state of rod-like molecular species (that is, molecules having a refractive index difference between the major axis and the minor axis) exhibiting liquid crystalline properties while curing the thin film of the photo-crosslinkable polymer liquid crystal material. At this time, molecular species extending in a direction coinciding with the polarization direction of the ultraviolet light among molecular species exhibiting liquid crystalline properties by ultraviolet light are crosslinked, and the alignment state is fixed in the same direction as the polarization direction. After the irradiation with ultraviolet light, the thin film of the photo-crosslinkable polymer liquid crystal material is annealed. Thereby, the molecular species exhibiting liquid crystalline properties of which the alignment state has not been changed by ultraviolet light are changed into liquid crystals, and the alignment state can be made to coincide with a polymer portion which has already been in a target alignment state, and the alignment state is fixed by subsequent cooling. That is, it is possible to obtain a wave plate configured with a thin film in which the orientation directions of most of molecular species exhibiting liquid crystalline properties and configuring a photo-crosslinkable polymer liquid crystal material are made to coincide with each other. In such a wave plate, the retardation can be adjusted by adjusting its thickness. The first wave plateand the second wave plateobtained in this manner are fixed to the lens memberby being respectively attached to the first optical surfaceand the second optical surfaceusing, for example, an adhesive. In the above description, the wave platesandare formed by applying the photo-crosslinkable polymer liquid crystal material onto the transparent resin base material, but the wave platesandmay be directly formed by applying it onto the optical surfacesandof the lens member.

124 224 124 224 A liquid crystal optical body such as the first wave plateand the second wave platecan also be manufactured by a method of manufacturing a liquid crystal optical body described in Japanese Patent Application Laid-Open No. 501147/2008. A liquid crystal optical body such as the first wave plateand the second wave platecan also be manufactured by a method described in https://www.jstage.jst.go.jp/article/oubutsu1932/70/9/70_9_1078/_pdf.

3 FIG. 124 224 124 224 21 21 21 21 124 1 21 21 224 2 21 21 124 21 224 21 124 224 124 224 21 21 21 21 124 224 124 224 a b a b a b a b a b a b With reference to, description will be given of a contrivance for manufacturing the first wave plateand the second wave plate. The retardation of the wave platesandvaries depending on the thickness of the liquid crystal layer. When the photo-crosslinkable polymer liquid crystal material is applied onto the optical surfacesand, a technique such as a spin coater is conceivable. However, since the liquid crystal material at the time of application contains a solvent and is low in viscosity, there is a concern that the film thickness of the liquid crystal material may become uneven in the optical surfacesand. However, with respect to the first wave plate, a liquid crystal material LLis spin-coated on the lens memberA in a state where the convex first optical surfacefaces upward, and with respect to the second wave plate, a liquid crystal material LLis spin-coated on the lens memberB in a state where the concave second optical surfacefaces upward. Thus, the first wave plateon the convex first optical surfacetends to become thin on the inner side and become thick on the outer side, and the second wave plateon the concave second optical surfacetends to become thick on the inner side and become thin on the outer side. As a result, a film thickness distribution of the first wave plateand a film thickness distribution of the second wave platecancel out each other, and the wave platesandas a whole can function as a uniform and accurate ¼ wave plate in the plane with respect to a direction perpendicular to an optical axis AX. When the viscosity of the liquid crystal material applied to the first optical surfaceand the viscosity of the liquid crystal material applied to the second optical surfaceare individually and appropriately adjusted even when the curvatures of the first optical surfaceand the second optical surfaceare largely different from each other, it is possible to cancel out the film thickness distribution between the wave platesand. Further, in the case of spin coating, it is possible to control a film thickness distribution in the lens surface by adjusting the rotation speed while considering the viscosity of the liquid crystal material, and it is easy to cancel out the film thickness distribution between the wave platesand.

2 FIG. 25 1 2 25 25 25 25 25 21 224 Referring back to, the polarizing optical elementis a wire grid polarizer, and selectively reflects first linearly polarized light Lin a first polarization direction corresponding to the Y direction that is the vertical direction or the perpendicular direction, and selectively transmits only second vertically polarized light Lin a second polarization direction corresponding to the X direction which is the horizontal direction. The polarizing optical elementhas a structure in which a large number of thin metal wires made of aluminum, nickel, or the like are arranged in parallel on a flexible transparent resin base material, for example, and a wire grid layer configured with the large number of thin metal wires is covered with a transparent protective layer. The polarizing optical elementreflects linearly polarized light having an electric field component (corresponding to the polarization direction) parallel to the direction in which the large number of thin metal wires extend and perpendicular to the periodic direction corresponding to the arrangement direction. The main body of the polarizing optical elementis manufactured by transferring the concavo-convex shape to the surface of a resin film formed of a UV resin or a thermoplastic resin using a mold having a concavo-convex structure, and then vapor-depositing aluminum on the top and side surfaces of convex portions of the concavo-convex shape from an oblique direction using a vacuum vapor deposition method. The main body of the polarizing optical elementcan also be manufactured by applying a polymer solution onto the mold having a concavo-convex structure using a spin coating method and curing the polymer solution formed at the surface of the mold (see, for example, JP-A-2011-221334). The polarizing optical elementobtained in this manner is fixed to the lens memberby being attached to the second wave plateusing, for example, an adhesive.

25 The polarizing optical elementmay not be a wire grid polarizer but may be, for example, a polarizer of a type in which a plurality of films provided with anisotropy by rolling are stacked.

4 FIG. 2 FIG. 10 1 1 1 20 10 22 22 124 21 224 21 124 224 1 1 25 25 1 25 1 224 124 21 124 22 1 2 2 22 21 124 224 2 25 21 22 21 21 25 21 25 2 20 20 100 Referring to, the image light ML emitted from the displaypasses through the polarizing control member PCand is converted into the right-handed circularly polarized light C. The image light ML of the right-handed circularly polarized light Cincident on the optical memberfrom the displaypartially passes through the reflective optical element, but is attenuated to approximately half the intensity at the time of transmission. The image light ML having passed through the reflective optical elementpasses through the first wave plate, passes through the lens member, and passes through the second wave plate. At this time, the image light ML is refracted by the lens memberand subjected to an action of being relatively converged by positive power. When the image light ML passes through the first wave plateand the second wave platein the forward direction, the image light ML is converted from the right-handed circularly polarized light Cinto the first linearly polarized light Lin the first polarization direction, and is incident on the polarizing optical element. The image light ML incident on the polarizing optical elementis efficiently reflected as the first linearly polarized light Lby the polarizing optical element, and is converted into the right-handed circularly polarized light Cby passing through the second wave plateand the first wave platefrom opposite directions when passing through the lens member. The image light ML emitted from the first wave plateis reflected by the reflective optical elementand is subjected to an action of being relatively converged by positive power, but is attenuated to approximately half of the intensity at the time of reflection. At this time, the image light ML is converted from the right-handed circularly polarized light Cinto left-handed circularly polarized light C. When the image light ML of the left-handed circularly polarized light Creflected by the reflective optical elementpasses through the lens member, the image light ML passes through the first wave plateand the second wave platein the forward direction, is converted into the second linearly polarized light Lin the second polarization direction, and is incident on the polarizing optical element. In the above, the image light ML reciprocates in the lens memberby being reflected by the reflective optical elementto pass through the lens membertwice, and consequently passes through the lens memberthree times. The image light ML incident on the polarizing optical elementvia the lens memberefficiently passes through the polarizing optical elementas the second linearly polarized light Lin the second polarization direction. The image light ML emitted to the outside of the optical memberis incident on the pupil position PP at which the eye EY of the wearer US is disposed in a collimated state by the converging action of the optical member(see). In other words, the wearer US wearing the first display deviceA can observe a virtual image of the image light ML.

103 103 21 11 21 11 1 21 2 21 a b b a b 2 FIG. In the case of the display optical systemsandshown in, since the second optical surfaceis concave, the light beam angle of the image light ML emitted from the image display panelcan be inclined inward, that is, toward the optical axis AX, and the material of the lens membercan have a margin in terms of the total reflection angle, and thus it is possible to increase the lens curvature and reduce the size of the image display paneland the entire optical system. Furthermore, a ratio between a curvature Rof the first optical surfaceand a curvature Rof the second optical surfacesatisfies the following relationship:

11 103 103 2 21 a b b Thus, the light beam angle of the image light ML emitted from the image display panelcan be made substantially parallel to a panel normal direction (direction parallel to the optical axis AX). Thereby, with respect to a video viewed by a user through the display optical systemsand, the image light ML emitted in the panel normal direction is incident on the eye EY, and thus it is possible to visually recognize a virtual image which is a display video without brightness or color unevenness. In particular, a curvature Rof the second optical surfaceis preferably 5 mm to 30 mm.

100 100 100 10 20 20 21 22 21 21 10 25 21 21 10 1 124 224 22 25 22 1 22 21 2 a b The virtual image display devicesA andB and the optical unitaccording to the first embodiment described above include the displaythat emits the circularly polarized image light ML, and the optical memberthat folds back the image light ML twice by reflection twice to form a virtual image. The optical memberincludes the lens member, the transmissive reflective optical elementthat is provided facing the first optical surfaceof the lens memberwhich is close to the display, the reflective polarizing optical elementthat is provided facing the second optical surfaceof the lens memberwhich is far from the displayand that reflects the image light ML, which is the first polarized light L, that is, linearly polarized light in the first polarization direction, and the wave platesandthat are provided between the reflective optical elementand the polarizing optical element, formed of a liquid crystal material such as a photo-crosslinkable polymer liquid crystal material, converts the image light ML having passed through the reflective optical elementinto the first polarized light L, that is, linearly polarized light in the first polarization direction, and converts the image light ML having been reflected by the reflective optical elementand reciprocating to pass through the lens membertwice into the second linearly polarized light Lin the second polarization direction.

124 224 124 224 21 21 124 224 21 21 124 224 21 21 124 224 21 21 a b a b a b a b In the virtual image display device, since the wave platesandare formed of a liquid crystal material such as a photo-crosslinkable polymer liquid crystal material, the film-shaped wave platesandmay be attached to the optical surfacesand, but the film-shaped wave platesandcan be directly formed at the optical surfacesand, and the birefringence characteristics of the wave platesandare easily set as desired. That is, even when the first optical surfaceand the second optical surfaceare curved surfaces, the birefringence characteristics of the wave platesandformed at these optical surfacesandare easily set as desired.

2 4 FIGS.and 25 1 25 1 124 224 25 The first polarization direction and the second polarization direction are directions for convenience, and specific definitions of the directions can be replaced. That is, in the examples shown in, the polarizing optical elementreflects the first polarized light Lin the first polarization direction which is the Y direction, but the polarizing optical elementmay reflect the first polarized light Lin the first polarization direction which is the X direction. In this case, the direction of the main axes of the wave platesandis adapted to match the polarizing optical element.

100 100 124 224 21 22 21 25 124 224 124 224 124 224 22 25 a b In the virtual image display devicesA andB according to the first embodiment, the wave platesandare separately provided between the first optical surfaceand the reflective optical elementand between the second optical surfaceand the polarizing optical element. Thereby, the film thickness distribution can be canceled out between the wave platesand, and the accuracy of the wave platesandcan be easily improved. The wave platesandare covered with the reflective optical elementand the polarizing optical element, and are prevented from being deteriorated due to an external environment.

100 100 21 21 21 22 100 100 10 20 21 11 21 21 20 a b a b b In the virtual image display devicesA andB according to the first embodiment, the first optical surfaceis a convex surface, and the second optical surfaceis a concave surface. When the first optical surfaceis a convex surface, the reflective optical elementcan have positive power, and the virtual image display devicesA andB can be easily miniaturized by reducing a distance between the displayand the optical member. When the second optical surfaceis a concave surface, the light beam angle of the image light ML emitted from the image display panelcan be inclined to the inner side, that is, the optical axis AX, and the refraction of the main light beam on the second optical surfaceof the lens membercan be reduced as a whole, making it easy to reduce the aberration of the optical member.

A virtual image display device and the like according to a second embodiment will be described below. The virtual image display device according to the second embodiment is provided by partially modifying the virtual image display device according to the first embodiment. Thus, description of portions common to the virtual image display device according to the first embodiment will not be omitted.

5 FIG. 20 22 21 3 11 22 21 21 3 24 25 21 24 21 21 21 25 a b b As shown in, an optical memberincludes a reflective optical element, a lens member, and a polarizing control member PCin order from an image display panelside. Here, the reflective optical elementis a transmissive mirror HM and is formed at a first optical surfaceof the lens member. The polarizing control member PCincludes a ¼ wave plateand a reflective polarizing optical elementin order from the lens memberside. That is, the ¼ wave plateis formed at a second optical surfaceof the lens memberso as to be interposed between the second optical surface, which is a curved surface, and the polarizing optical element.

6 FIG. 5 FIG. 103 1 20 10 22 21 21 24 24 1 25 25 1 25 24 24 1 22 21 22 1 2 2 22 24 21 24 2 25 25 25 2 a is a conceptual diagram showing optical operations of a first display optical systemshown in. In this case, image light ML of right-handed circularly polarized light Cincident on the optical memberfrom the displaypartially passes through the reflective optical elementand is incident on the lens member. The image light ML having passed through the lens memberpasses through the ¼ wave platein the forward direction. The image light ML having passed through the ¼ wave platein the forward direction is converted into first linearly polarized light Lin a first polarization direction, and is incident on the polarizing optical element. The image light ML incident on the polarizing optical elementis efficiently reflected as the first linearly polarized light Lby the polarizing optical elementand passes through the ¼ wave platein the opposite direction. The image light ML having passed through the ¼ wave platefrom the opposite direction is converted into right-handed circularly polarized light C, is incident on the reflective optical elementvia the lens member, is reflected by the reflective optical element, and is subjected to an action of being relatively converged by positive power. At this time, the image light ML is converted from the right-handed circularly polarized light Cinto left-handed circularly polarized light C. The image light ML of the left-handed circularly polarized light Creflected by the reflective optical elementpasses through the ¼ wave platein the forward direction via the lens member. The image light ML having passed through the ¼ wave platein the forward direction is converted into second linearly polarized light Lin a second polarization direction, and is incident on the polarizing optical element. The image light ML incident on the polarizing optical elementefficiently passes through the polarizing optical elementas the second linearly polarized light Lin the second polarization direction.

24 3 20 20 In the case of the present embodiment, the ¼ wave plateis provided in the polarizing control member PC, and it is sufficient to provide a single wave plate in the optical member, making it possible to simplify the manufacturing process of the optical member.

A virtual image display device and the like according to a third embodiment will be described below. The virtual image display device according to the third embodiment is provided by partially modifying the virtual image display device according to the first embodiment. Thus, description of portions common to the virtual image display device according to the first embodiment will not be omitted.

7 FIG. 20 2 21 25 11 2 22 24 24 21 21 21 22 a a As shown in, an optical memberincludes a polarizing control member PC, a lens member, and a reflective polarizing optical elementin order from an image display panelside. The polarizing control member PCincludes a reflective optical elementand a ¼ wave plate. That is, the ¼ wave plateis formed at a first optical surfaceof the lens memberso as to be interposed between a first optical surface, which is a curved surface, and the reflective optical element.

24 2 20 20 24 21 21 24 24 24 21 21 21 24 a a a a a In the case of the present embodiment, the ¼ wave plateis provided in the polarizing control member PC, and it is sufficient to provide a single wave plate in the optical member, making it possible to simplify the manufacturing process of the optical member. In this case, when the ¼ wave plateis formed at the first optical surface, an in-plane distribution may be positively applied to the thickness of a liquid crystal material applied onto the first optical surface. In the case of the present embodiment, the angle of the image light ML passing through the ¼ wave platechanges and increases depending on an image height which is a distance from an optical axis AX, and when the thickness of the liquid crystal material on the peripheral side is reduced in accordance with such a change in the passing angle, it is possible to enhance the uniformity of the function of the ¼ wave platein the plane of the ¼ wave plateand to curb the occurrence of ghost light. As a method of adjusting the thicknesses of the liquid crystal material, it is conceivable to adjust the thickness of the liquid crystal material applied onto the first optical surfaceby using, for example, an inkjet. That is, the amount of liquid crystal material applied onto the first optical surfaceis adjusted by the inkjet, and UV irradiation is performed on the spot. Thereby, it is possible to provide liquid crystal films having different thicknesses in the plane on the first optical surface, form different phase difference distributions at respective positions in the plane, and to uniformize the function of the ¼ wave platewith respect to the image light ML.

A virtual image display device and the like according to a fourth embodiment will be described below. The virtual image display device according to the fourth embodiment is provided by partially modifying the virtual image display device according to the first embodiment. Thus, description of portions common to the virtual image display device according to the first embodiment will not be omitted.

8 FIG. 103 21 121 221 24 a As shown in, in a first display optical system, a lens memberis a meniscus lens having positive power as a whole, and includes a first lensand a second lens, which are bonded together via a ¼ wave plate.

21 121 21 221 24 21 21 24 21 c d c d An optical surfaceon the emission side of the first lensis a concave surface, an optical surfaceon the incidence side of the second lensis a convex surface, and the curvatures of both are the same. In this case, the ¼ wave platehas a shape conforming to the optical surface, which is a curved surface, and the optical surface. That is, the ¼ wave plateis embedded in the lens member.

9 FIG. 8 FIG. 103 1 20 10 22 21 121 24 1 221 25 25 1 25 24 24 1 22 1 2 2 22 21 24 2 25 25 25 2 a is a conceptual diagram showing optical operations of the first display optical systemshown in. In this case, image light ML of right-handed circularly polarized light Cincident on the optical memberfrom a displaypartially passes through a reflective optical elementand is incident on the lens member. The image light ML having passed through the first lenspasses through the ¼ wave platein the forward direction to be converted into the first linearly polarized light Lin the first polarization direction, and passes through the second lensto be incident on the polarizing optical element. The image light ML incident on the polarizing optical elementis efficiently reflected as the first linearly polarized light Lby the polarizing optical elementand passes through the ¼ wave platein the opposite direction. The image light ML having passed through the ¼ wave platefrom the opposite direction is converted into right-handed circularly polarized light Cto be incident on the reflective optical element. At this time, the image light ML is converted from the right-handed circularly polarized light Cinto left-handed circularly polarized light C. When the image light ML of the left-handed circularly polarized light Creflected by the reflective optical elementpasses through the lens member, the image light ML passes through the ¼ wave platein the forward direction, is converted into the second linearly polarized light Lin the second polarization direction, and is incident on the polarizing optical element. The image light ML incident on the polarizing optical elementefficiently passes through the polarizing optical elementas the second linearly polarized light Lin the second polarization direction.

121 221 121 221 121 221 24 24 24 24 In the case of the present embodiment, a liquid crystal material such as a photo-crosslinkable polymer liquid crystal material can be applied to one of the first lensand the second lens, and a liquid crystal material such as a photo-crosslinkable polymer liquid crystal material can be sealed between the lensesand. In this case, one of the first lensand the second lensserves as a base material, and the other serves as a cover lens. Thereby, there is no possibility that the ¼ wave platewill come into contact with a user's hand, and the periphery of the ¼ wave plateis sealed with an adhesive or the like to prevent moisture from entering the ¼ wave plate, thereby making it easy to curb the deterioration of the ¼ wave plate.

121 221 In addition, when the first lensand the second lenshave different refractive indices, a lens effect can be produced between glass materials, which can lead to a further increase in resolution and a further reduction in size, thickness, and weight of the entire optical system.

A virtual image display device and the like according to a fifth embodiment will be described below. The virtual image display device according to the fifth embodiment is provided by partially modifying the virtual image display device according to the first embodiment. Thus, description of portions common to the virtual image display device according to the first embodiment will not be omitted.

10 FIG. 103 21 20 21 21 24 25 21 24 25 20 21 24 25 21 24 21 a a b b b b. As shown in, in a first display optical system, a lens memberof an optical memberis a plano-convex lens. A first optical surfaceis a spherical surface or an aspherical surface. In this case, since a second optical surfaceis a flat surface, even when a ¼ wave plateand a polarizing optical elementare attached to the lens member, the ¼ wave plateand the polarizing optical elementbefore being attached to the optical memberdo not need to have flexibility and do not need to be deformed in accordance with the second optical surface. Thus, the ¼ wave plateand the polarizing optical elementcan be formed at a non-resin-based substrate such as glass. In addition, the second optical surfaceis a flat surface, and thus it is relatively easy to adjust the thickness of a liquid crystal material when the ¼ wave plateis directly formed at the second optical surface

24 21 22 21 a The ¼ wave platemay be formed at the first optical surfaceand on the inner side of a reflective optical element, or may be formed inside the lens member.

103 103 10 20 a b In the case of the display optical systemsandshown in the drawing, FOV120° is achieved, and a distance from the displayto an emission surface at the rear end of the outer edge of the optical memberis 14.8 mm.

A virtual image display device and the like according to a sixth embodiment will be described below. The virtual image display device according to the sixth embodiment is provided by partially modifying the virtual image display device according to the first embodiment. Thus, description of portions common to the virtual image display device according to the first embodiment will not be omitted.

11 FIG. 103 21 20 21 21 21 21 a a b a b As shown in, in a first display optical system, a lens memberof an optical memberis a biconvex lens. A first optical surfaceand a second optical surfaceare spherical surfaces or aspherical surfaces. When the first optical surfaceand the second optical surfaceare curved surfaces, it is easy to reduce aberration.

24 21 22 21 a A ¼ wave platemay be formed at the first optical surfaceand on the inner side of a reflective optical element, or may be formed inside the lens member.

103 103 10 20 a b In the case of the display optical systemsandshown in the drawing, FOV120° is achieved, and a distance from a displayto an emission surface at the rear end of the center of the optical memberis 14.9 mm.

These are descriptions of the present disclosure with reference to the embodiments. However, the present disclosure is not limited to the embodiments described above. It is possible to implement the present disclosure in various modes without departing from the spirit of the disclosure. For example, the following modifications can be made.

21 20 In the above-described embodiments, the lens memberincorporated into the optical memberis merely an example, and one or two lenses may be included in a bonded state or a separated state.

20 10 20 Although not essential, the optical memberis preferably at least FOV100°, and a distance from the displayto an emission surface at the rear end of the center of the optical memberis preferably 20 mm or less.

200 100 100 Although it has been assumed above that the HMDis worn on the head and is used, the virtual image display devicesA andB may also be used as a hand-held display that is not worn on the head and is to be looked into like binoculars. That is, in the present disclosure, the head-mounted display also includes a hand-held display.

124 224 21 21 a b. The first wave plateand the second wave plateare not limited to the photo-crosslinkable polymer liquid crystal material, but may be various liquid crystal materials, and may be attached onto the first optical surfaceor the second optical surface

4 FIG. 10 25 The polarization state shown inand the like is an example, and for example, the image light ML emitted from the displaycan be left-handed circularly polarized light, and in this case, the polarizing optical elementneeds to selectively reflect only vertically polarized light in a polarization direction corresponding to the X direction which is the horizontal direction and to selectively transmit linearly polarized light in a polarization direction corresponding to the Y direction which is the vertical direction.

A first virtual image display device according to a specific aspect includes a display that emits circularly polarized image light, and an optical member that folds back the image light twice by reflection to form a virtual image, in which the optical member includes a lens member, a transmissive reflective optical element that is provided facing a first optical surface of the lens member which is close to the display, a reflective polarizing optical element that is provided facing a second optical surface of the lens member which is far from the display and reflects image light, which is linearly polarized light in a first polarization direction, and a wave plate that is provided between the reflective optical element and the polarizing optical element, is formed of a liquid crystal material, converts the image light having passed through the reflective optical element into linearly polarized light in a first polarization direction, and converts the image light, which is reflected by the reflective optical element to reciprocate, into linearly polarized light in a second polarization direction.

In the virtual image display device, since the wave plate is formed of the liquid crystal material, it is easy to attach the film-shaped wave plate to the optical surface, or it is not necessary to attach the film-shaped wave plate to the optical surface, and thus it is possible to directly form the film-shaped wave plate on the optical surface, and the birefringence characteristics of the wave plate are easily set as desired. For example, even when the first optical surface and the second optical surface are curved surfaces, the birefringence characteristics of the wave plates formed at these optical surfaces are easily set as desired.

In the virtual image display device according to the specific aspect, the liquid crystal material is a photo-crosslinkable polymer liquid crystal material. In this case, the wave plate is manufactured more easily and accurately.

In the virtual image display device according to the specific aspect, the photo-crosslinkable polymer liquid crystal material is an ultraviolet-curable photo-crosslinkable polymer liquid crystal material. In this case, the photo-crosslinkable polymer liquid crystal material layer applied onto the optical surface or a light-transmitting resin base material is irradiated with ultraviolet light, and thus it is possible to control the alignment state of molecular species exhibiting liquid crystalline properties while curing the photo-crosslinkable polymer liquid crystal material layer.

In the virtual image display device according to a specific aspect, the wave plate is formed by irradiating a thin film, which is formed of the photo-crosslinkable liquid crystal material, with ultraviolet light having a controlled polarization state and annealing the thin film. In this case, the molecular species of which the alignment state has not been changed by ultraviolet light are changed into liquid crystals, and the alignment state thereof can be made to coincide with the molecular species which have already been in a target alignment state.

In the virtual image display device according to a specific aspect, the wave plate is provided between the second optical surface and the polarizing optical element.

In the virtual image display device according to the specific aspect, the wave plate is provided between the first optical surface and the reflective optical element.

In the virtual image display device according to a specific aspect, the wave plate is separately provided between the first optical surface and the reflective optical element and between the second optical surface and the polarizing optical element.

In the virtual image display device according to a specific aspect, the wave plate is embedded in the lens member.

In the virtual image display device according to the specific aspect, the polarizing optical element is a reflective polarizer having a wire grid layer. In this case, the polarizing optical element can be attached onto the optical surface, and even when the optical surface is a curved surface, it is relatively easy to form the polarizing optical element on the optical surface.

In the virtual image display device according to the specific aspect, the first optical surface is a convex surface. In this case, the reflective optical element can have positive power, and the virtual image display device can be easily miniaturized by narrowing an interval between the display and the optical member.

In the virtual image display device according to the specific aspect, the second optical surface is a concave surface. In this case, the refraction of the main light beam on the second optical surface of the lens member can be reduced as a whole, and the aberration of the optical member can be easily reduced.

A second virtual image display device according to a specific aspect includes a display that emits circularly polarized image light, and an optical member that folds back the image light twice by reflection to form a virtual image, in which the optical member includes a lens member, a transmissive reflective optical element that is provided facing a first optical surface of the lens member which is close to the display, a reflective polarizing optical element that is provided facing a second optical surface of the lens member which is far from the display and reflects image light, which is linearly polarized light in a first polarization direction, and a wave plate that is provided between the reflective optical element and the polarizing optical element, is formed in a layer shape on a curved optical surface of the lens member, converts the image light having passed through the reflective optical element into linearly polarized light in a first polarization direction, and converts the image light, which is reflected by the reflective optical element to reciprocate, into linearly polarized light in a second polarization direction.

In the second virtual image display device according to a specific aspect, the wave plate is formed by being applied onto the curved optical surface of the lens member.

An optical unit according to a specific aspect includes a display that emits circularly polarized image light, and an optical member that folds back the image light twice by reflection to form a virtual image, in which the optical member includes a lens member, a transmissive reflective optical element that is provided facing a first optical surface of the lens member which is close to the display, a reflective polarizing optical element that is provided facing a second optical surface of the lens member which is far from the display and reflects image light, which is linearly polarized light in a first polarization direction, and a wave plate that is provided between the reflective optical element and the polarizing optical element, is formed of a liquid crystal material, converts the image light having passed through the reflective optical element into linearly polarized light in a first polarization direction, and converts the image light, which is reflected by the reflective optical element to reciprocate, into linearly polarized light in a second polarization direction.